1. Field of the Invention
This invention relates to a demolition agent for demolishing brittle materials, such as rock or concrete, and more particularly to a demolition agent for demolishing brittle materials by means of expansive stress, the demolition agent being filled in a hole drilled in the mass of brittle material in the form of a slurry so as to be allowed to expand by hydration.
2. Prior Art
Various demolition methods have hitherto been known for statically demolishing a block of brittle material, such as rock or concrete, wherein the block is drilled to form a hole into which a slurry of expansive material is filled and then allowed to stand for expansion to demolish the block by means of expansive stress.
For example, it has been tried to use quick lime as a demolition agent because it exerts an intensive expansion force upon hydration. However, when the quick lime is used singly, it begins to hydrate and expand immediately after it is mixed with water to lower the fluidity of the mixture rapidly to such degree that the mixture is hardly poured into the hole. This is because the hydration speed of the quick lime is too high. The quick lime slurry has another disadvantage that it tends to spout out of the pouring port due to a so-called gunshot phenomenon, resulting in unsatisfactory exhibition of demolition effect, even though it might be poured into the hole.
In order to obviate the aforementioned disadvantages of the known quick lime slurry, improved powder compositions have been proposed and used by mixing the same with water to form pastes which are poured into holes drilled in rocks or concrete blocks. One of these prior made proposals is disclosed by Japanese Patent Public Disclosure No. 142894/1980, and comprises a mineral powder composition added with a water-reducing agent, said mineral powder composition being prepared by mixing limestone, silica and calcium sulfate in a defined ratio followed by baking to form CaO particles included or surrounded by 3CaO.SiO.sub.2 crystal grains. Japanese Patent Public Disclosure No. 67059/1981 discloses another improved composition which comprises a hard-burned quick lime powder having a crystal size of not less than 10 microns, for example 20 to 30 microns, and added with a hydraulic material and a modifying agent. However, these compositions are disadvantageous in that an excessively long time is required for them to exhibit their demolishing effect, particularly when the environmental temperature is low to decelerate the reaction speed of quick lime and to depress the expansive pressure. For instance, a time period of more than 14 hours, generally 2 to 3 days, is required for demolition at a temperature of lower than 10.degree. C. and a time period of more than 3 days, generally more than one week, is required when the environmental temperature approximates to 0.degree. C. Another disadvantage involved in the latter-mentioned composition is that the hard-burned quick lime contained therein must be burned at a high temperature ranging from 1300.degree. to 1600.degree. C. for 2 to 7 days. Such a severe burning condition required for the preparation of the composition raises significant operational and economical problems.